Furnace for manufacturing ingots or bars of metal or alloys, particularly bars of uranium carbide



June 18, 1968 A. ACCARY ET AL 3,388,903

FURNACE FOR MANUFACTURING INGOTS OR BARS OF METAL OR ALLOYS PARTICULARLY BARS OF URANIUM CARBIDE Filed Dec. 7, 1964 3 Sheets-Sheet 2 r 43 7 I I A! A) 66 INVENTOES fllvae HCCARY Auae TAEILLOU BY JEAN 77zouv June 18. 1968 A. ACCARY ETAL.

FURNACE FOR MANUFACTURING INGOTS 0R BARS OF HETAL 0R ALLOYS. PARTICULARLY BARS 0F URANIUM CARBIDE F1106 DOG- 7. 1964 r IIIlI/l J."

' IIIIIIIP NVVINTDPS United States Patent Claims. (31. 266-33) ABSTRACT OF THE DISCLOSURE The present disclosure relates to electron beam furnaces for manufacturing ingots or bars of metal, particularly bars of uranium carbide. An electron beam furnace of the instant type generally comprises an enclosure having vacuum pumping means attached thereto. Within this enclosure is a bottomless double walled crucible of a cylindrical shape which diverges at the upper end to receive and contain metal. A head, vertically movable within the cylinder, and means for controlling the movement thereof constitute the base of the furnace. One or more electron beams are directed into the upper open end of the casting crucible to heat metal therein. The furnace also includes means for circulating a coolant fluid in the double wall of the crucible and a system for supplying the material to be melted, in granular form.

The present invention relates particularly to an improved means for regulating the supply of material to the furnace. According to the invention the vacuum within the enclosure which houses the melting crucible is measured by means of a cold cathode gauge. The movement of a vibrating apron which feeds the granules of material to the crucible is automatically controlled in response to the measured vacuum in order to precisely control the furnace feed rate.

The aim of the invention is to render automatic the supply of the furnace with materials so as to subject them to fusion, in such a way as to reduce the handling costs and to ensure the functioning of the furnace in economical manner.

According to the invention, the system for supply of granules or of consumable electrodes of the materials to be fused is fitted with means for regulating the consumption governed by a control means sensitive to the degree of the vacuum which exists in the enclosure where the crucible is located.

According to one embodiment, the control means sensitive to the degree of the vacuum which exists in the enclosure where the crucible is located, comprises a cold cathode gauge with means for measuring the intensity of the ionisation current.

Other characteristics of the invention will be evident from the description which follows and from the attached drawing which show, by way of example, one embodiment of an improved furnace according to the invention.

In the drawings:

FIGURE 1 shows diagrammatically a sectional view of the assembly of the furnace,

FIGURE 2 shows diagrammatically a sectional view, but on a large scale, the system for supply of granules of the material to be melted.

FIGURE 3 is a diagram showing the governing means of the supply system at the pressure of the enclosure where the crucible is located, and

FIGURE 4 shows diagrammatically in section the supply system of consumable electrodes constituting the material to be melted.

3,388,903 Patented June 18, 1968 P ce The furnace for manufacturing bars of uranium carbide, shown in FIGURE 1, comprises a crucible 1 without a base, with double walls cooled by a liquid 4 circulated by any known suitable means (not shown). Said crucible is of cylindrical form and its upper part diverges conically. A vertically movable head 6, located below the crucible 1, constitutes initially the base of the latter. The vertical movement of the movable head 6 is ensured by means, for example, of a system comprising a transmission by a screw 17 engaged in the rotatable nut, forming part of a reduction assembly 16 actuated by an electrical motor 18.

The heating means of the furnace are constituted for example by an electron gun 10, in which exists a suitable vacuum maintained by a device 14, the beam of electrons being directed on the surface of the bath in the cruci ble 1.

The raw material, in the form of granules of uranium carbide 7, is fed into the crucible by means of a supply device shown generally as 8 and fitted with an outlet spent 9. p

The furnace assembly is housed within a sealed enclosure 12, in which a suitable vacuum is maintained by means of an appropriate device shown by 13.

In FIGURE 2, the supply device 8 has been shown in greater detail, which device comprises a hopper 20 opening out above a vibrating-apron 21 which is mounted, in an inclined position, on oscillating levers such as 21a, 21b, and the lower end of which is located above the inlet of the spout 9. The oscillating movement of the apron 21 is ensured by an electro-magnet 23 in combination with a return spring 22.

The feed rate of the particles 7 is substantially propor tional to the amplitude of the oscillations of the apron and said latter are controlled by the value of the energising voltage of the electro-magnet 23, which may be varied between nil and 220 volts in the example.

A first control means for the installation consists in connecting the feed rate of the granules supplied with the degree of vacuum which exists in the enclosure where the furnace is located, i.e. to the value of the low pressure of said enclosure.

The measurement of the pressure in this enclosure is effected by a cold cathode gauge 41 (FIGURE 3), or which the value of the intensity of the ionisation current is measured, which is connected to the pressure.

The measurement of this intensity is effected by a microammeter 42, with which is connected in series, for the transmission of the controlling signals, another microammeter or galvanometer with contacts 43. Preferably, said galvanometer has a sensitivity adjustable by means of a variable shunt (not shown).

The movable member of the galvanometer 43 has been diagrammatically shown as 44, and as 45 and 46, two adjustable contacts arranged in the adjacent zones of the two ends of the measuring scale, and suitable for determining a working zone.

The electro-magnet 23, which controls the vibrating belt 21 (see also FIGURE 2), may be supplied selectively, either from a source of current ST at volts, for example or from a source RT with a higher voltage, 220 volts for example.

The feeding by the source of current ST at 110 volts is effected by means of a regulating rheostat 48 and the moving contact 49 of an electronic relay 51, driven by means of maximum contact 46 of the galvanometer 43. The feeding by the source RT at 220 volts is effected in a first condition, by means of a resting contact 54 of the electronic relay 51 at the maximum and by means of a resting contact 55 of another electronic relay at the minimum 56, energised by the contact 45 of the galvanometer 43 and by a row-transformer 58 fitted with a manual controlling member 59 while, in another condition, the

said electro-magnet 23 is supplied, from the main source T at 220 volts directly by the resting contact 54 of the electronic at the maximum 51 and by a moving contact 61 of the minimum electronic relay 56 without passing by means of the roto-transformer 58.

The functioning is as follows:

For an average vacuum in the enclosure of the furnace, the feed rate of the supply system is average. This means that, when the movable element 44 of the contact galvanometer 43 is located in an intermediate position, such as, for example, that shown on FIGURE 3, the electromagnet 23 is fed from the source RT at 220 volts by means of two resting contacts 54 and 55 of the two electronic relays 51 and 56 and by means of the roto-transformer 58 regulated to a position corresponding to the amplitude which the electro-magnet 23 must have for the average feed rate under consideration for the supply system.

It the vacuum in the enclosure of the furnace falls below a predetermined value, i.e. if the pressure in this enclosure exceeds a predetermined, corresponding maximum value, for which the limiting contact 46 of the galvanometer 43 is adjusted, the maximum electronic relay 51 is energised and the electro-magnet 23 is then fed through the moving contact 49 of said relay, from the source of voltage ST at 110 volts only, which causes a corresponding reduction in the feed rate of the supply system.

On the other hand, for a vacuum exceeding an extreme, predetermined value, i.e. when the pressure in the enclosure falls below the value corresponding to the lower end contact 45 of the galvanometer 43, it is the minimum electronic relay 56 which is energised, so that the electro-magnet 23 is supplied, this time, by means of the resting contact 54 of the maximum electronic relay 51 and of the moving contact 61 of the minimum electronic relay 56 with the full voltage of 220 volts of the source RT. Consequently the feed rate of the supply system must increase.

In the case of a furnace with consumable electrode (FIG. 4) the advance of said electrode 110 is also controlled as a function of the vacuum existing in the enclosure 12. The electrode 110 is fixed on a movable support 111 traversing in a sealed manner a chamber 112 connected at 14 to a vacuum pump. Above the chamber 112 is provided an advancing means 113 for the support 111. Said advancing means 113 is controlled by the electro-magnct 23 (FIG. 3), as is the case of the supply device for granules 8. The electrode 110 and the crucible 1 are connected to a voltage source, which causes an electric arc to be formed between the end of the electrode 110 and the crucible, so that the electrode 110 melts in proportion with its advancement.

Of course, the invention is not limited to the embodiment described and shown and one may add thereto numerous modifications, without departing from the scope of the invention.

We claim:

1. A furnace for manufacturing metal ingots from a metallic material including,

a vacuum enclosure surrounding a crucible adapted to confine a bath of molten metal,

supply means connected with said enclosure to feed said metallic material to said crucible,

control means connected to said supply means to automatically regulate the feed rate of said material, sensing means attached to said enclosure for detecting the level of vacuum therein, and

electrically actuated switch means connected to said control means and operated in response to an electrical signal from said sensing means for governing said control means.

2. A furnace as described in claim 1 wherein said sensing means comprises a cold cathode gauge and means for supplying an electrical signal to said switch means which is proportional to the ionization current of said gauge.

3. A furnace as described in claim 2 wherein said supply means comprises a supply apron for delivering granular metallic material from a hopper to said crucible,

said supply apron being connected to electromagnetic means adapted to be selectively energized in response to said electrical signal to vibrate said apron at a variable frequency in order to regulate the feed rate of said material.

4. A furnace as described in claim 3 wherein said switch means includes first relay means operated in response to a predetermined maximum level of pressure in said enclosure for reducing the feed rate of said material, and

second relay means operated in response to a predetermined minimum level of pressure in said enclosure for increasing the feed rate of said material.

5. A furnace as described in claim 2 wherein said supply means comprises a support vertically movable within a chamber over said crucible and adapted to hold a consummable electrode of said metallic material,

said support and said crucible adapted to be energized by a suitable source of voltage in order to sustain an electric are between said electrode and said bath of molten metal,

propelling means connected to an upper portion of said support for advancing said electrode towards said bath and,

said control means comprising electromagnetic means connected to said propelling means.

References Cited UNITED STATES PATENTS 4/1959 Brennan 16464 7/1957 Garmy 164-49 

